Pancreatitis is the most common significant complication of endoscropy retrograde cholangiopancreatography (ERCP). There are no effective modalities to prevent post-ERCP pancreatitis. Platelet activating factor (PAF) has been shown to be an important early inflammatory mediator in experimental pancreatitis. Endogenously, it is degraded by PAF- acetyl hydrolase. PAF-AH, given exogenously, has been shown to attenuate injury in experimental pancreatitis. A recombinant PAF-AH has been given to humans and appears to be safe. We plan to study rPAF-AH in preventing post-ERCP pancreatitis in a double-blinded, placebo controlled, prospective trial.